(* Copyright (c) 1993-1997, Silicon Graphics, Inc.
 * ALL RIGHTS RESERVED 
 * Permission to use, copy, modify, and distribute this software for 
 * any purpose and without fee is hereby granted, provided that the above
 * copyright notice appear in all copies and that both the copyright notice
 * and this permission notice appear in supporting documentation, and that 
 * the name of Silicon Graphics, Inc. not be used in advertising
 * or publicity pertaining to distribution of the software without specific,
 * written prior permission. 
 *
 * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
 * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
 * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
 * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
 * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
 * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
 * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
 * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
 * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
 * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
 * 
 * US Government Users Restricted Rights 
 * Use, duplication, or disclosure by the Government is subject to
 * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
 * (c)(1)(ii) of the Rights in Technical Data and Computer Software
 * clause at DFARS 252.227-7013 and/or in similar or successor
 * clauses in the FAR or the DOD or NASA FAR Supplement.
 * Unpublished-- rights reserved under the copyright laws of the
 * United States.  Contractor/manufacturer is Silicon Graphics,
 * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
 *
 * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
 *)

(*  unproject.ml
 *  When the left mouse button is pressed, this program 
 *  reads the mouse position and determines two 3D points 
 *  from which it was transformed.  Very little is displayed.
 *)

(* Ported from C to OCaml by Florent Monnier *)

open GL
open Glu
open Glut

let display() =
  glClear [GL_COLOR_BUFFER_BIT];
  glFlush();
;;


(* Change these values for a different transformation  *)
let reshape ~width:w ~height:h =
  glViewport 0 0 w h;
  glMatrixMode GL_PROJECTION;
  glLoadIdentity();
  gluPerspective 45.0 (float w /. float h) 1.0 100.0;
  glMatrixMode GL_MODELVIEW;
  glLoadIdentity();
;;


let mouse ~button ~state ~x ~y =
  match button with
  | GLUT_LEFT_BUTTON ->
      if state = GLUT_DOWN then begin
        let viewport = glGetInteger4 Get.GL_VIEWPORT in
        let a, b, c, d = viewport in  let viewport = [| a; b; c; d |] in
        let mvmatrix = glGetMatrix Get.GL_MODELVIEW_MATRIX in
        let projmatrix = glGetMatrix Get.GL_PROJECTION_MATRIX in
        (*  note: viewport.(3) is height of window in pixels  *)
        let realy = viewport.(3) - y - 1 in  (*  OpenGL y coordinate position  *)
        Printf.printf "Coordinates at cursor are (%4d, %4d)\n%!" x realy;
        (*  returned world x, y, z coords  *)
        let wx, wy, wz =
          gluUnProject (float x) (float realy) 0.0
              mvmatrix projmatrix viewport
        in
        Printf.printf "World coords at z=0.0 are (%f, %f, %f)\n%!" wx wy wz;
        let wx, wy, wz =
          gluUnProject (float x) (float realy) 1.0
              mvmatrix projmatrix viewport
        in
        Printf.printf "World coords at z=1.0 are (%f, %f, %f)\n%!" wx wy wz;
      end

  | GLUT_RIGHT_BUTTON ->
      if state = GLUT_DOWN then
        exit(0);
  | _ -> ()
;;


let keyboard ~key ~x ~y =
  match key with
  | '\027' ->  (*escape *)
      exit(0);
  | _ -> ()
;;

(* 
 *  Open window, register input callback functions
 *)
let () =
  let _ = glutInit Sys.argv in
  glutInitDisplayMode [GLUT_SINGLE; GLUT_RGB];
  glutInitWindowSize 500 500;
  glutInitWindowPosition 100 100;
  let _ = glutCreateWindow Sys.argv.(0) in
  glutDisplayFunc ~display;
  glutReshapeFunc ~reshape;
  glutKeyboardFunc ~keyboard;
  glutMouseFunc ~mouse;
  glutMainLoop();
;;

